1. Technical Field
The present invention relates in particular to a double seal bearing including a pair of sealing plates of a non-contacting type on at least one side thereof, and more particularly to a double seal ball bearing especially suitable for a spindle motor of a hard disk drive.
2. Description of the Prior Art
The bearing illustrated in FIG. 11 includes a non-contacting type of sealing structure of the prior art.
This non-contacting type of sealing structure of the prior art includes at least on one end thereof a sealing plate 11. This sealing structure is of the non-contacting type in which the outer peripheral edge of the sealing plate 11 is secured on the end surface of the outer race 2, whereas the inner peripheral edge of this sealing plate is separated from the outer peripheral surface of the inner race 1.
A disadvantage inherent in the non-contacting type of bearing is that the grease contained within the bearing and dust or other contaminant produced within the bearing tend to flow out through the clearance formed at the non contacting portion of the bearing while the inner or outer race is rotated.
In general, the following countermeasures have been taken to eliminate the above mentioned disadvantage.
(1) One of the countermeasures is to make the inner peripheral edge 12a of the sealing plate contact with the outer peripheral surface of the inner race 1 as shown in FIG. 12.
(2) The other of the countermeasures is to provide an oil seal (the seal of contacting type) or a labyrinth seal mechanism of non-contacting type for avoiding the flowing out of the grease or dusts.
However, the following problems or disadvantages are present in these countermeasures.
(1) As for the bearing including a sealing structure of the contacting type in which the inner peripheral edge of the sealing plate contacts with the inner race, there are the problems listed below:
(a) a torque is generated due to the friction between elements;
(b) wear is produced on the contacting portion (especially on the inner peripheral edge of the sealing plate) during the utilization of the bearing. This leads to the leakage of the grease and the production of the dusts or particles due to wear; and
(c) the material which can be employed for the sealing plate is limited to rubber materials or resinous materials. This leads to limitations on applications for the bearing.
(2) As for the bearing including a sealing structure such as the oil seal (the seal of contacting type), or the bearing including a sealing structure of the non-contacting type such as the labyrinth seal mechanism, there is a substantial common problem that additional space is required for providing such sealing means. This is an essential problem for the equipment necessitating the miniaturization thereof. In addition, the cost for manufacturing the bearing is also increased.
In the case of the bearing adapted to be used in the spindle motor of the hard disk drive means, the function of the magnetic disk is affected seriously, if wear particles produced during rotation flow into the magnetic disk portion.
In recent years, various sealing means are proposed for preventing the particles produced within the bearing from flowing out of the bearing.
In these sealing means, although it is necessary to provide a sealing effect similar to that had been obtained by the bearing including a sealing means of contacting type, such bearing can not be adopted since it produces wear particles at the sealing contacting portion between elements.
In this connection, following structures for sealing have been adopted:
the structure in which a bearing including a sealing plate of non-contacting type at the one side thereof is used together with an additional labyrinth mechanism;
the structure in which a bearing including a sealing plate of non-contacting type at the one side thereof is used together with an additional magnetic fluid sealing mechanism; and
the structure in which a bearing including a sealing plate of non-contacting type at the one side thereof is used together with an additional magnetic fluid sealing mechanism and a labyrinth mechanism.
In these structures, additional space is required for installing such additional sealing mechanisms as mentioned above.
Additionally, the distance between bearings (bearing span) is insufficient for eliminating the harmonic vibration due to the lack of the accuracy of the rotation of the motor hub and the rigidity of assembly. The stability of the rotation is not assured. Further, it is difficult to substantially prevent the particles within the bearing from flowing out into the disk portion.
Accordingly, the object of the present invention is to improve and ascertain the non-contacting sealing function by providing dual labyrinth mechanism through incorporating an additional labyrinth mechanism into the bearing of prior non-contacting type including at the one side thereof a sealing plate.
Another object of the present invention is to provide a multi purpose bearing which can be employed not only as a bearing of inner race rotating type, but also as a bearing of outer race rotating type.
In order to achieve these and other objects, the basic structure of the bearing of the present invention includes an inner race, an outer race, and rotating bodies interposed therebetween. The bearing is provided with at least one side thereof a pair of annular inner and outer sealing plates having a central opening respectively so as to remain a slight clearance between each plate and one of the inner and outer races respectively to assure the labyrinth seal function.
Each side portion of the inner race is provided with a stepped contour including an inner shoulder of smaller diameter and an outer shoulder of larger diameter. Each side portion of the outer race is also provided with a stepped contour including an inner shoulder of smaller diameter and an outer shoulder of larger diameter. Each side portion of the bearing is adapted to be closed by a pair of annular sealing plates. Each of these plates is provided with a central opening respectively. The embodiments of the bearing of the present invention will now be described as follows.
 less than The First Embodiment of the Invention greater than 
The outer peripheral portion of the inner sealing plate is secured on an inner shoulder of the outer race with leaving a slight clearance between the inner peripheral surface of the sealing plate and an inner shoulder of the inner race. Thus, the sealing plate and the inner race are prevented from contacting with each other, and a labyrinth seal function can be obtained. The inner peripheral portion of the outer sealing plate is secured by any adhesive on the outer shoulder of the inner race with leaving a slight clearance between the outer peripheral surface of the sealing plate and the outer shoulder of the outer race so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Second Embodiment of the Invention greater than 
The inner peripheral portion of the inner sealing plate is secured by any adhesive on the inner shoulder of the inner race with leaving a slight clearance between the outer peripheral surface of the sealing plate and the inner shoulder of the outer race so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained. The outer peripheral portion of the outer sealing plate is secured by any adhesive on the outer shoulder of the outer race with leaving a slight clearance between the inner peripheral surface of the sealing plate and the outer shoulder of the inner race so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Third Embodiment of the Invention greater than 
The outer peripheral portion of the inner sealing plate is secured by any adhesive on the inner shoulder of the outer race with leaving a slight clearance between the inner peripheral surface of the sealing plate and the inner shoulder of the inner race so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained. The outer peripheral portion of the outer sealing plate is also secured by any adhesive on the outer shoulder of the outer race with leaving a slight clearance between the inner peripheral surface of the sealing plate and the outer shoulder of the inner race so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Fourth Embodiment of the Invention greater than 
The inner peripheral portion of the inner sealing plate is secured by any adhesive on the inner shoulder of the inner race with leaving a slight clearance between the outer peripheral surface of the sealing plate and the outer shoulder of the inner race so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained. The inner peripheral portion of the outer sealing plate is also secured by any adhesive on the outer shoulder of the inner race with leaving a slight clearance between the outer peripheral surface of the sealing plate and the outer shoulder of the outer race so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Fifth Embodiment of the Invention greater than 
The inner race of this embodiment includes only one shoulder, and the inner peripheral portion of the inner sealing plate is secured thereon by any adhesive with leaving a slight clearance between the outer peripheral surface of the sealing plate and the inner shoulder of the outer race so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained. The diameter of the inner peripheral portion of the outer sealing plate is same as or larger than the diameter of the shaft bearing bore of the inner race. The outer peripheral portion of the outer sealing plate is secured by any adhesive on the outer shoulder with leaving a slight axial clearance between the end surface of the inner race and the surface of the outer sealing plate opposing thereto so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Sixth Embodiment of the Invention greater than 
The outer peripheral portion of the inner sealing plate is secured by any adhesive on the inner shoulder of the outer race with leaving a slight clearance between the inner peripheral surface of the sealing plate and the shoulder of the inner race so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained therebetween. The diameter of the inner peripheral portion of the outer sealing plate is same as or larger than the diameter of the shaft bearing bore of the inner race. The outer peripheral portion of the outer sealing plate is secured by any adhesive on the outer shoulder with leaving a slight axial clearance between the end surface of the inner race and the surface of the outer sealing plate opposing thereto so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Seventh Embodiment of the Invention greater than 
The outer race includes only one shoulder, and the outer peripheral portion of the inner sealing plate is secured thereon by any adhesive with leaving a slight clearance between the inner peripheral surface of the sealing plate and the inner shoulder of the inner race so as to prevent the sealing plate and the inner race from contacting with each other. Thus the labyrinth seal function can be obtained. The diameter of the outer peripheral portion of the outer sealing plate is same as or smaller than that of the outer race. The inner peripheral portion of the outer sealing plate is secured by any adhesive on the outer shoulder with leaving a slight axial clearance between the end surface of the outer race and the surface of the outer sealing plate opposing thereto so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained.
 less than The Eighth Embodiment of the Invention greater than 
The outer race includes only one shoulder, and the outer diameter of the outer sealing plate is same as or slightly smaller than that of outer race. The inner peripheral portion of the inner sealing plate is secured on the inner shoulder of inner race by any adhesive with leaving a slight clearance between the outer peripheral surface of the sealing plate and the shoulder of the outer race so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained. The inner peripheral portion of the outer sealing plate is secured by any adhesive on the outer shoulder of inner race with leaving a slight axial clearance between the end surface of the outer race and the surface of the outer sealing plate opposite thereto so as to prevent the sealing plate and the outer race from contacting with each other. Thus the labyrinth seal function can be obtained.
The advantages of the present invention
The following advantages can be obtained by a pair of sealing plates of non-contacting type incorporated into the end portion or portions of the bearing per se.
(a) The sealing effect will be increased substantially relative to the bearing of the prior art including one sealing plate of the non-contacting type.
(b) The leakage of the grease contained in the bearing through the non-contacting portion of the sealing plate can be avoided, and the performance on the rotation of the bearing can be improved.
(c) The conventionally required space for installing the labyrinth seal additionally to the bearing no longer necessary.
(d) It is possible to make the equipment employing the bearing of the present invention compact, to reduce the space required for installing the bearing, and to decrease the cost for making the equipment.
(e) It is possible to substitute the bearing of the present invention for the bearing of the prior art of contacting type, for the purpose of increasing the reliability.
(f) In the case that the double seal bearing of the present invention is incorporated into the motor of the hard disk drive means, particles within the bearing are prevented from flowing into the magnetic disk by means of the labyrinth seal function of the bearing. In this connection, it is not necessary to provide additional labyrinth seal and/or magnetic fluid seal. Further, it is also possible to increase the bearing span. In conclusion, the disadvantages or problems associated with the bearing of the prior art can be eliminated once and for all by the present invention.